The present invention relates to a planar inverted-F antenna (PIFA) and the application system thereof, and more particularly, to the planar inverted-F antenna formed on a surface of a circuit base board and the application system thereof.
With the advances in communication technologies, the applications using communication technologies have also increased significantly, thus making the related products more diversified. Especially, consumers have more demands on advanced functions from communication applications, so that many communication applications with different designs and functions have been continuously appearing in the market, wherein the computer network products with wireless communication functions are the main streams recently. Moreover, with integrated circuit (IC) technologies getting matured, the size of product has been gradually developed toward smallness, thinness, shortness and lightness.
An antenna in the communication products is an element mainly used for radiating or receiving signals. Particularly, the design and study of microstrip antennas or printed antennas are quite important. An antenna is an element used for radiating or receiving electromagnetic wave, and generally, the features of antenna can be known by the parameters of operation frequency, radiation patterns, reflected loss, and antenna gain, etc.
According to different operation requirements, the functions equipped in the communication products are not all the same, and thus there are many varieties of antenna designs used for radiating or receiving signals, such as a rhombic antenna, a turnstile antenna, a triangular microstrip antenna, and an inverted-F antenna, etc. The structure of a conventional inverted-F antenna basically includes a small piece of metal plate installed on a ground plane to be a radiating main body, and a short-circuit line that is added on the edge of the radiating main body and connected to the ground plane, so that the length of antenna is reduced from xc2xd resonance wavelength to xc2xc resonance wavelength, thus achieving the effect of miniaturizing the antenna size.
Referring to FIG. 1A and FIG. 1B, FIG. 1A and FIG. 1B are 3-D schematic diagrams respectively showing two conventional planar inverted-F antennas. Such as shown in FIG. 1A, one conventional planar inverted-F antenna is composed of a ground plane 10, a radiating metal line 20, a short-circuit line 22 and a TEM transmission line 30, wherein one end of the short-circuit line 22 is vertically connected to one end of the radiating metal line 20, and the other end of the short-circuit line 22 is vertically connected to the ground plane 10. The TEM transmission line 30 is composed of an inner conductor 34 and an outer conductor 32, wherein the inner conductor 34 is vertically connected to the radiating metal line 20 for feeding signals. Further, such as shown in FIG. 1B, in the other conventional planar inverted-F antenna, a radiating metal plate 40 and a short-circuit plate 42 are used to replace the radiating metal line 20 and the short-circuit line 22. However, those two conventional planar inverted-F antennas are formed three-dimensionally, which means that they have to occupy the space resulted from such as the height of the short-circuit line 22 or the height of the short-circuit plate 42. Therefore, the aforementioned space taken by the conventional planar inverted-F antennas becomes a very difficult issue for designing an ultra-thin product.
Hence, there is an urgent need to develop a modified planar inverted-F antenna for satisfactorily meeting the antenna requirements of small size, small thickness, high gain, broad bandwidth, simple design, and low cost, etc., thereby overcoming the disadvantages of the conventional planar inverted-F antennas.
In view of the invention background described above, in the wireless communication products, an antenna plays an important part, since the antenna has great influence on the performance of communication performance. Therefore, the design of the antenna is developed towards the aspects of small size, low cost, high gain and easy practice. Since the conventional planar inverted-F antennas occupy certain space in height, they fail to effectively satisfy the requirements of communication products, especially for the products having ultra-small thickness.
It is the principal objective of the present invention to provide a planar inverted-F antenna and the application system thereof, thereby providing the antenna with ultra-small thinness, small size, good quality and low price, wherein the antenna of the present invention also has excellent antenna features of broad bandwidth, low antenna loss and good radiation patterns, etc., and can be easily matched with a circuit base board for fabricating a communication product, thereby lowering the cost needed for integrating with the circuit and enhancing the product stability, thus having high industrial application value.
It is the other objective of the present invention to provide a planar inverted-F antenna and the application system thereof, for obtaining better antenna performance by simultaneously installing two planar inverted-F antennas on a base board via the arrangement of antenna diversity.
In accordance with the aforementioned objectives of the present invention, the present invention provides a planar inverted-F antenna, wherein the planar inverted-F antenna comprises: a base board at least having a first surface and a second surface, wherein the first surface and the second surface are located respectively on two opposite sides of the base board; a circular hole penetrating the base board, wherein the circular hole has a first radius; a slot penetrating the base board, the slot having a first straight side and a second straight side that are parallel to each other, wherein both ends of the first straight side and both ends of the second straight side are respectively connected to a first arc and a second arc that are mirror-reflected to each other, and the convex surface of the first arc and the convex surface of the second arc face outwards, the first arc and the second arc being formed with a second radius; a first radiating conducting line located on the first surface of the base board, and are formed conformally around portion of the circular hole, wherein the first radiating conducting line has an inner side located near the circular hole, and an outer side located farther away from the circular hole; a second radiating conducting line, wherein the second radiating conducting line is located on the first surface, and is formed conformally around portion of the first arc and portion of the first straight side; and a straight radiating conducting line located between the first arc and the circular hole, wherein one end of the first radiating conducting line adjacent to the slot is connected to one end of the straight radiating conducting-line, and one end of the second radiating conducting line adjacent to the first arc is merged into portion of the outer side adjacent to the aforementioned end of the first radiating conducting line, the straight radiating conducting line and the first radiating conducting line forming an opening, the second side of the slot being located at the same side of the opening, the first side of the slot being located at the side different from the opening.
Further, the present invention provides a planar inverted-F antenna application system, the application system comprising: a base board at least having a first surface and a second surface, wherein the first surface and the second surface are located respectively on two opposite sides of the base board, a first planar inverted-F antenna formed on the first surface of the base board, wherein a straight conducting line of the first planar inverted-F antenna and the radiating conducting line surrounding portion of a circular hole are combined to form a first opening; and a second planar inverted-F antenna formed on the first surface of the base board, wherein a straight conducting line of the second planar inverted-F antenna and the radiating conducting line surrounding portion of a circular hole are combined to form a second opening. The first planar inverted-F antenna is parallel to the second planar inverted-F antenna, wherein the opening direction of the first opening can be the same as, opposite to or reversed to the opening direction of the second opening.